bindings: Add empty checks for toV8()

Source/bindings/core/v8/Iterable.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef Iterable_h
 #define Iterable_h
 
 #include "bindings/core/v8/V8IteratorResultValue.h"
 #include "bindings/core/v8/V8ScriptRunner.h"
 #include "core/dom/Iterator.h"
@@ skipping 46 matching lines @@
             KeyType key;
             ValueType value;
 
             if (!source->next(scriptState, key, value, exceptionState))
                 return;
 
             ASSERT(!exceptionState.hadException());
 
             args[0] = toV8(value, creationContext, isolate);
             args[1] = toV8(key, creationContext, isolate);
+            if (args[0].IsEmpty() || args[1].IsEmpty()) {
+                if (tryCatch.HasCaught())
+                    exceptionState.rethrowV8Exception(tryCatch.Exception());
+                return;
+            }
 
             v8::Local<v8::Value> result;
             if (!V8ScriptRunner::callFunction(v8Callback, scriptState->executionContext(), v8ThisArg, 3, args, isolate).ToLocal(&result)) {
                 exceptionState.rethrowV8Exception(tryCatch.Exception());
                 return;
             }
         }
     }
 
     class IterationSource : public GarbageCollectedFinalized<IterationSource> {
@@ skipping 114 matching lines @@
 public:
     Iterator* iterator(ScriptState* scriptState, ExceptionState& exceptionState)
     {
         return this->entriesForBinding(scriptState, exceptionState);
     }
 };
 
 } // namespace blink
 
 #endif // Iterable_h